1. Field of the Invention
The present invention relates to optical information processing, and more particularly, to a method for detecting a pattern of an over-sampling image and an optical information processing apparatus and method using the same, which can detect a specific pattern such as a mark from an image of a datapage detected using a covariance.
2. Description of the Related Art
Examples of optical information processing apparatuses include compact discs (CDs), digital versatile discs (DVDs), high-definition DVDs (HD-DVDs), blue-ray discs (BDs), and near-field optical processing apparatuses. With a recent increase in demand for a next-generation storage system with a large storage capacity, attentions are focused on a holographic optical information processing apparatus.
For recording of optical information in a holographic optical information processing apparatus, a recording reference beam and an information beam carrying image information of original data are irradiated onto an optical information recording medium in an overlapping manner and the resulting interference pattern is recorded on the optical information recording medium.
For reproduction of the recorded optical information, a reproducing reference beam is irradiated onto the optical information recording medium and a reproducing beam is generated by diffraction of the reproducing reference beam by the interference pattern. If the recording reference beam is identical to the reproducing reference beam, the generated reproducing beam carries optical information identical to the optical information carried in the information beam in the recording operation.
The holographic optical information processing apparatus processes digital data on a page-by-page basis, and such page-based data is generally called a datapage. That is, the holographic optical information processing apparatus processes information on a datapage-by-datapage basis.
An image of a datapage reproduced from the reproducing beam is detected by a light-receiving array device such as a complementary metal-oxide semiconductor (CMOS) device or a charge-coupled device (CCD). The detected image of the datapage is restored to the original data through a series of demodulating and decoding processes.
Also, in general, the datapage is generated by various over-sampling methods such as a 1:3 over-sampling method, a 1:2 over-sampling method, and 1:1.5 over-sampling method.
The over-sampling method detects an image of a datapage using detection pixels more than data pixels at a given ratio, and samples suitable data from the over-sampling detection image.
For example, the 1:3 over-sampling method detects an image of a datapage by constructing an optical system such that nine (3×3) detection pixels correspond to one data pixel, and samples values of the detection pixels on the over-sampling detection image through a suitable sampling process.
Herein, the sampling process may be any sampling process such as a sampling process of sampling each of only values of detection pixels detecting an image of the most accurate data pixel on the detection image, or a sampling process of adding values of nine detection pixels corresponding to the respective data pixels and averages the results to perform a sampling operation.
The datapage recorded by the above mapping method includes a data region with data information and a mark disposed to detect the position and range of the data region. Herein, the mark has a specific pattern in which a plurality of on-pixels and off-pixels are arranged in consecutively or inconsecutively.
In reproducing the data, a portion corresponding to the mark on the detected image of the datapage is first detected and a detection portion of the data region within a predetermined range from the position is detected to sample a data value. That is, the frame mark serves as an identifier for detecting the sampling position.
However, in reproducing the image of the datapage, because the position of a reproducing image formed in a light-receiving array device changes due to the shrinkage or rotation of an optical information storage medium, a misalignment occurs, thus causing a mismatch between a pixel of the datapage image (hereinafter simply referred to as a pixel) and a pixel of the light-receiving array device (hereinafter simply referred to as a detection pixel).
The present invention provides a method for detecting a pattern of an over-sampling image and an optical information processing apparatus and method using the same, which can detect a specific pattern such as a mark from an image of a datapage detected using a covariance.